A liquid crystal display device utilizes optical anisotropy, dielectric anisotropy and so forth of liquid crystal molecules in a liquid crystal composition. A classification based on an operating mode for the liquid crystal molecules includes a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a bistable twisted nematic mode (BTN), an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a fringe field switching (FFS) mode and a vertical alignment (VA) mode.
A liquid crystal display device having a mode in which a polymer is combined with the liquid crystal composition is known. Specific examples thereof include a polymer sustained alignment (PSA) mode or a polymer stabilized (PS) mode. In the liquid crystal display device having the mode, the liquid crystal composition to which a polymerizable compound is added is injected into the display device. The display device is irradiated with UV light in a state in which voltage is applied between electrodes, and the polymerizable compound is polymerized to form the polymer in the liquid crystal composition. The liquid crystal device is obtained in which a response time of the device is shortened, and image persistence is improved by the above method.
The above method above is applicable to the liquid crystal display devices having various operating modes, and such modes are known as a PS-TN mode, a PS-IPS mode, a PS-FFS mode, a PSA-VA mode and a PSA-OCB mode. The polymerizable compound used in the device having such a mode is considered to have high capacity for aligning liquid crystal molecules, but solubility in the liquid crystal composition is far from high. An attempt has been made so far on improving the solubility in the liquid crystal composition. However, if the solubility is improved, polymerization reactivity tends to reduce. Accordingly, a development has been desired for the polymerizable compound having a suitable balance between the solubility and the polymerization reactivity.